is there an easy way to detect if the entire contents of one list are in another?

if I have a list like this: li = [1,2]
and I have another which will have random values, I want the program to do something only if every value of li is in the second list.

I need a way to program this:

``````x = random.randint(0,10)
y = random.randint(0,10)
li = [1,2]
li2 = [x,y]

if every value of li2 is in li:
do this``````

## All 4 Replies

Hi!

I don't know if you would call this easy, but it seems to work:

``````def is_sublist( lst1, lst2 ):
for elem in lst1:
if elem not in lst2:
return False
return True``````

e.g.:

``````l1 = [1,2]
l2 = [2,4,6]
l3 = [1,2,3]
print is_sublist(l1, l2)   # --> False
print is_sublist(l1, l3)   # --> True``````

If you use sets instead of lists, there is a builtin function:

``````s1 = set([1,2])
s2 = set([2,3,4])
s3 = set([1,2,3])
print s1.issubset(s2)
print s2.issubset(s3)``````

Hope this helps.

Regards, mawe

You can use type()

``````x = random.randint(0,10)
y = random.randint(0,10)
li = [1,2]
li2 = [x,y]

test_list = []
if every_value of li2 is in li:
if type(every_value) == type(test_list) :
do this``````

Note that 'of li2 is in li' will compare entire list to list, not each element, assuming every_value is a list. It is not considered good code practice to use the letters 'el', 'eye', or 'oh' for variable names as they look too much like numbers and are confusing.

is there an easy way to detect if the entire contents of one list are in another?

if I have a list like this: li = [1,2]
and I have another which will have random values, I want the program to do something only if every value of li is in the second list.

I need a way to program this:

``````x = random.randint(0,10)
y = random.randint(0,10)
li = [1,2]
li2 = [x,y]

if every value of li2 is in li:
do this``````

if your lists comparing only numbers, you can sort them first?

``````if sorted(li) == sorted(li2):
do something``````

This will not work because list a and b are not the same length ...

``````a = [1, 2]
b = [2, 3, 6, 1]
# this will not work here ...
if sorted(a) == sorted(b):
print 'a is in b'
else:
print 'a is not in b'``````

Using set() will work, like mawe said ...

``````a = [1, 2]
b = [2, 3, 6, 1]
# this will work ...
if set(a).issubset(set(b)):
print 'a is in b'
else:
print 'a is not in b'``````

The next approach is pretty universal ...

``````def is_a_in_b(a, b):
"""returns True if all elements in list a are in list b, else False"""
ax = []
for x in a:
for y in b:
if x == y:
ax.append(y)
return a == ax

print is_a_in_b([1, 2], [2, 3, 6, 1])      # True
print is_a_in_b([1, 2], [1, 3, 7, 9, 4])  # False``````
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